The present invention refers to an IVC rack system and a method for detecting infectious particles within an IVC rack system and more specifically to the improvement of microbiological monitoring of laboratory mice, gerbils, hamsters and rats or other laboratory animals housed under specific sterile conditions.
In the field of experimental medicine and laboratory animal science, IVC rack systems (IVC: Individually Ventilated Microisolator-Cages) are used for housing test animals such as laboratory mice, gerbils, hamsters and rats. In IVC rack systems, the test animals are supplied with sterile air to improve the test results performed with the test animals. Specific pathogen-free (SPF) laboratory mice and rats gain rapidly increasing importance in basic and applied biomedical research. The breeding and housing of SPF-mice, gerbils, hamsters and rats or other laboratory animals requires germ-free environment and a defined climate for the animals within the barrier system. The IVC cages represent a set of individual microbarrier cages, which facilitate housing of test animals in a specific pathogen-free containment.
FIG. 1 shows a conventional IVC rack system in principle. In this conventional IVC rack system, ambient room air is drawn by a ventilator through a pre-filter for absorbing particles and then through a HEPA-particle filter (HEPA: High.Efficiency Particle Absorber) via an inlet blower and is finally distributed to the individual IVC cages. The IVC cages are supplied individually with sterile air through a manifold and supply specific air-supply diffusers which are mounted on the IVC cages. The IVC cages contain test animals for biomedical investigations. The test animals breath the sterile air and produce exhaust air which is passively conveyed or drawn by a ventilator to a particle filter unit or to the building exhaust system. The particle filter unit shown in FIG. 1 comprises a pre-filter, the ventilator and a HEPA-filter filtering the exhaust air generated by the test animals within the IVC cages. The filter exhaust air can then be reintroduced into the rack system or output into the ambient room.
FIG. 2 shows the conventional IVC rack system according to the prior art in more detail. As can be seen from FIG. 2, the IVC rack system according to the prior art comprises a plurality of IVC cages within different rows. The sterile supply air is transferred via a vertical supply plenum to different horizontal supply air manifolds connected to the IVC cages. The exhaust air of the IVC cages within a row are output via a horizontal exhaust air manifold.
In an IVC rack system, all IVC cages are supplied individually with the sterile supply air, and there is no exchange of air between the IVC cages. For performing biomedical investigations, the test animals within the IVC cages have to be taken out by the investigating scientist. During the investigation of the test animals, it is possible that the investigated test animals will be infected with viruses, bacteria or parasites. The infected animals will be put back into the IVC cage and infect further test animals. Another possibility for infecting the test animals is a defect input particle filter unit which does not generate sterile supply air. The exchange of laboratory test animals with other laboratories is another source for possible infections of test animals. A still further possibility is that the test animals are already infected when put initially into the IVC cage. These latent infected test animals will either develop an overt or acute infection and disease and infect the other test animals within the same IVC cage.
Since there is no air exchange between the IVC cages, a monitoring of the experimental test animal colony by investigating sample animals taken from different IVC cages is not helpful, because infections within other IVC cages remain undetected. In the case of new infections of test animals in the IVC rack system, there is a high risk that the infection of the test animal colonies spreads during handling and bedding changes before being detected.
Accordingly, it is an object of the present invention to provide an IVC rack system and a method for detecting infectious particles within any cage of an IVC rack system, wherein infections within the IVC rack system are detected within a very short period of time.
This object is achieved with an IVC rack system having the features of main claim 1 and by a detection method comprising the features of claim 13.
The invention provides an IVC rack system comprising
a plurality of IVC cages for test animals which is supplied with sterile air,
wherein samples of exhaust air from the IVC cages are supplied from sampling points to at least one sentinel cage housing sentinel animals as bio-indicators for the detection of infectious particles within the exhaust air samples.
In a preferred embodiment, the sentinel animals act as bio-indicators for the detection of infectious pathogens.
These infectious pathogens are preferably air-born pathogens.
The IVC cages and the sentinel cages comprise in a preferred embodiment pressure gauges to control the air pressure within the IVC rack system.
In a further preferred embodiment of the IVC rack system according to the present invention, the sentinel cages comprise an input air-flow regulation faucet to regulate the influx of exhaust air samples into the sentinel cage.
In a further preferred embodiment, the sentinel cages comprise each an output air-flow regulation faucet to regulate the outflow of exhaust air from the sentinel cage.
The sterile air is preferably supplied via manifolds and enters the IVC cages by air-supply diffusers mounted on the IVC cages.
In a preferred embodiment, an input particle filter unit for generating sterile air is provided comprising a pre-filter which is supplied with ambient room air and a HEPA-filter connected to the pre-filter to generate sterile air from the pre-filtered ambient room air.
In a still further preferred embodiment of the IVC rack system according to the present invention, an output particle filter unit is provided comprising a pre-filter which filters the exhaust air from the IVC cages and the exhaust air from the sentinel cage and a HEPA-filter connected to the pre-filter.
The test animals and the sentinel animals are preferably laboratory mice, gerbils, hamsters or rats.
In a preferred embodiment of the IVC rack system according to the present invention the IVC rack system is a single sided IVC rack system.
In an alternative preferred embodiment of the IVC rack system according to the present invention the IVC rack system is a double sided IVC rack system.
In a preferred embodiment of the IVC rack system according to the present invention, a sampling point is provided at every row of the IVC cages within the IVC rack system.
In a further preferred embodiment of the IVC rack system according to the present invention a sampling point is provided at the vertical exhaust plenum of the IVC rack system.
In an alternative embodiment, a sampling point is provided at each IVC cage of the IVC rack system.
This provides the advantage that the exact location of the source of infection within the IVC rack system can be detected.